docs: three dangling links, and a gate so they cannot accumulate

The vault is the project's source of truth, so a link to a page that does not
exist is a promise the repo cannot keep. Three were dangling:

- Dankclaw/Gitea.md pointed twice at dankclaw/compose.yaml — **which this
  session retired**. The clean cutover obligation from my own change: the page
  now describes the unit that publishes 3000 and the canonical Caddy unit, and
  records why the compose file is gone.
- Dankclaw/Hermes-Dashboard.md linked [[LAN DNS]]; the page is [[LAN-DNS]].
- LLM/frank-medium-radiance-mxfp4.md linked [[Observability on Dankclaw]]; the
  page is [[Observability]].

scripts/check-vault-links.py + a seam keep it that way. The checker models
Obsidian's rules, which took three corrections to get right — and each was a
false positive that would have sent me editing healthy docs:

  1. Wikilinks are case-insensitive. A case-sensitive matcher reported 45
     breaks; 39 were `[[qBittorrent]]` vs qbittorrent.md.
  2. `[[folder/Note]]` resolves by path suffix, not by stem.
  3. `%20` in a markdown link is URL-encoding, not a filename.

Validating the linter against the resolver it models is the prerequisite for
trusting any of its output — the same discipline that caught a bad assertion of
my own earlier tonight.

tests/docs_completeness.bats

@@ -33,3 +33,13 @@ load helpers
         }
     done < <(find "$REPO_ROOT/serverAppConfigs-docs" -name '*.md' -not -name 'index.md' -not -path '*/.obsidian/*' | sort)
 }
+
+@test "no unresolved links in the docs vault" {
+    # A wikilink to a page that does not exist is a promise the repo cannot
+    # keep. Fixing the three that were dangling (2026-09-16) also meant
+    # retiring a reference to dankclaw/compose.yaml, which no longer exists.
+    # The checker models Obsidian's resolution rules; see its docstring for
+    # the three false-positive classes a naive version produces.
+    run "$REPO_ROOT/scripts/check-vault-links.py" "$REPO_ROOT/serverAppConfigs-docs"
+    [ "$status" -eq 0 ] || { echo "$output"; false; }
+}